Project Summary [Abstract]: Waitlist mortality for patients awaiting lung transplantation is unacceptably high in the US. On the other hand, we are only utilizing 20% of the donor lungs being offered for transplantation. This is significantly lower than other countries in Europe (Up to 50%) with similar post-transplant outcomes. This low utilization is attributed to the stringent and inconsistent donor selection criteria across the centers in US. There are at least 15 different donor variables to consider, and the significance of each variable and the interplay between variables is currently unknown. Unlike other solid organs, kidney for example, there is currently no unified donor risk stratification system for lung transplantation. Additionally, many of the criteria used by centers have individually been challenged, utilizing large national and international databases, with evidence that selecting donors outside the standard criteria does not have a significant effect on post-transplant outcomes. Additionally, some European and North American centers have shown success with extended criteria donors at an institutional level; however it has not been widely demonstrated comprehensively at a national level. The goal of this project is to develop a comprehensive donor risk scoring system to quantify risk associated with combinations of various donor factors. This will enable standardization of donor selection and improvement in donor utilization for lung transplantation around the US. The positive impact of a donor risk score system on utilization and transplantation for difficult-to-match patients has already been shown in kidney transplantation. Secondly, we aim to determine outcomes of lung transplants utilizing various donor and recipient risk combinations (virtual match). With this match, we hope to identify donors that are currently underutilized and demonstrate acceptable outcomes when they were utilized in reality and in virtual match. This has a potential to impact overall lung transplant candidate outcomes by both increasing organ utilization rates and by transplanting recipients before they deteriorate and become either unsuitable for transplant or higher risk recipients.